Since the introduction of the automatic, or the stepless transmission, hydrodynamic torque converters have been the connecting link between a driving motor and the true transmission gear train. A torque converter enables, first, a comfortable and jerk-free travel through a slip range and simultaneously damps lapses of rotational uniformity of the internal combustion motor. Second, the basic principal of torque maximizing makes available a substantial torque for startup.
In accordance with the state of the technology, a hydrodynamic torque converter consists of a pump impeller, a turbine gear, the reaction member (guide rod, stator) and the necessary oil for torque transmission.
With the present state of the technology, torque converters are known which incorporate a converter bypass clutch and a primary clutch, whereby the primary clutch (PK) shifts between the motor and the converter and the converter bypass clutch operates between the motor and the transmission.
EP 09 16 043, of the Applicant discloses a control system for a continuous transmission with a torque converter and a converter bypass clutch, wherein the control of the converter bypass clutch follows a strategy in which the torque converter is considered to be a hydrodynamic variator in a series connection with the continuous transmission and the shift in or shift out of the converter bypass clutch, is exclusively a function of rotational speed of the motor. Thereby, particularly, an excessive turning speed of the motor upon the starting operation and a decrease of rotational speed during tractive running are to be avoided.
Upon the closing of the converter bypass clutch, that is to say, upon the connection of the motor with the transmission, the motor rotational speed would normally decrease even with a constant pressure on the gas pedal. This is an unexpected event for the driver and the riding comfort is impaired.
The present invention has the purpose of making a method available for the prevention of a decreasing motor rotational speed upon the closing of the torque converter clutch in a continuously variable transmission with a variator and a hydrodynamic torque converter in order that, in this manner, the stated disadvantages of the state of the technology are avoided and the comfort of the driver is increased.